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Hole where you don't want one
#216504 10/02/08 12:22 am
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I'm sure I know the answer but..... I need to split the cases again don't I
[Linked Image]
I'n going to my room now to sulk tired


I can fix any thing with a bigger hammer
64-71 Triumph Bitsa
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Re: Hole where you don't want one
John Michl #216507 10/02/08 1:11 am
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If I'm not mistaken, that there is a hole in your piston! And part of that aluminum is now floating around inside your motor. I would tear it apart and clean/inspect thoroughly.

Any idea what happened? It may just be the lighting, but that piston looks like it has less carbon buildup on it, like that side was running leaner. With a single carb head, that surprises me, unless you're just burning more oil on the other side. Detonation perhaps? Or was it caused by a collision with the intake valve? Or should I just shut up and let you grieve in peace? blush

John

Re: Hole where you don't want one
John M #216517 10/02/08 2:00 am
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I don't think it hit the valve (but what do i know) I guess it was lean, but with a single carb ? John can you point me in a direction so it doesn't happen again?


I can fix any thing with a bigger hammer
64-71 Triumph Bitsa
Re: Hole where you don't want one
John Michl #216518 10/02/08 2:01 am
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BTW tere is the head
[Linked Image]


I can fix any thing with a bigger hammer
64-71 Triumph Bitsa
Re: Hole where you don't want one
John Michl #216527 10/02/08 2:44 am
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def looks like detenation, you can see pitting on the head and the valve face. the piston does not look like it hit anything but is eaten away from detenation. something weird going on for sure electrical wise.


ROB HALL
HCV MOTORSPORTS
Re: Hole where you don't want one
John Michl #216530 10/02/08 2:54 am
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Jm, is there any evidence of an air leak on the head gasket? Jack

Re: Hole where you don't want one
John Michl #216531 10/02/08 2:58 am
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Jm, is there any evidence of an air leak on the head gasket? Jack

Re: Hole where you don't want one
Jack Adams #216533 10/02/08 3:14 am
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timing way retarded for that cylinder or are you using electronic wasted spark arrangement?
Alan

Re: Hole where you don't want one
ACWilkins #216547 10/02/08 7:31 am
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Air leak on 1 to 2 inlet manifold or bad points/timing set-up if applicable?

Sorry to see that John...

Blapper redwine

Re: Hole where you don't want one
Blapper #216565 10/02/08 11:12 am
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With single carb, you tune so neither cylinder is weak, even if that sometimes means one is slightly rich.

Almost got to be timing or mixture. Your pistons look like normal 9:1. Not using a soft grade of plugs are you?


Amateur Loctite enthusiast.
Re: Hole where you don't want one
triton thrasher #216566 10/02/08 11:18 am
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Err, have you checked your oil level?


1971 Triumph T100C
1974 Honda XL350
1982 Suzuki GS750T
2000 Honda VFR800FI
Re: Hole where you don't want one
triton thrasher #216585 10/02/08 12:24 pm
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Read this from the engineer that designed the Cadilac's NorthStar engine and you will re-examine the idea that the damage was caused by detonation.

http://www.contactmagazine.com/Issue54/EngineBasics.html

John

Re: Hole where you don't want one
John Healy #216606 10/02/08 2:37 pm
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Info, Its a low compression engine 650cc 1971 with a Boyer and tampanium, it was using Champion N3c plugs, it was timed with Boyer instructions and strobed. A AMAL 930 with a new 106 needle jet a new needle in the 2nd notch and a 230 main jet.
Now I'm not a engineer. That article tells me more than I can comprehend (maybe, I'll read it again). I just don't want or need to make this error again so any help will be welcomed


I can fix any thing with a bigger hammer
64-71 Triumph Bitsa
Re: Hole where you don't want one
John Michl #216610 10/02/08 3:25 pm
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Thanks for that link, John. For now I think I understand it, I wonder how long it will last. Pinging is the sound you hear that is caused by detonation, and whilst bad doesn't usually cause immediate damage (though it describes the piston damage in my motor failure 20,000 miles ago) while pre-ignition shows up as a dead motor with a hole in the piston and is caused by hot spots in the combustion chamber that ignite the mixture way before the spark would.

Unfortunately I can't see John's pictures. But having a name for the cause of the damage isn't quite the same as being able to prevent it in the future.

I thought it was interesting that Bonnevilles produce more HP/in. cubed than a Northstar engine if you can believe factory HP specs.



Ed
1970 Bonneville
Re: Hole where you don't want one
John Michl #216635 10/02/08 5:09 pm
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Originally Posted by John Michl
I'm sure I know the answer but..... I need to split the cases again don't I ?


John -
The answer to your question is "No". As a line mechanic at the southeast's largest Triumph dealership, I repaired numerous bikes in this condition back in the 60's and 70's.

1) What you will need to do is remove the sump plug and wash the bottom end with mineral spirits and blow out with compressed air. That will get all the big chunks and at least 99% of the small stuff.

2) Then, IF you don't have an oil filter, drain the oil tank and wash out the particulate matter on the bottom. This can be done with the tank on the frame.

3) Then fit an oil filter on the return line before cranking the bike, if you don't already have one. Even a temporary unit strapped on top of the gearbox would be a BIG advantage.


Yes, you may suffer from debris in the return oil pump before the oil system is completely clean. That's a very small gamble. But it's sure is a lot less expensive and a lot less work doing things this way. You're certainly not going to do any engine damage if your clean up is even moderately well done.

Try to remember that we're working on an engine that has more in common with your lawn mower than any F1 racing engine. Also keep in mind that your high detergent oil is going to take all the microscopic bits to the oil filter within the first 30-60 miles.

If your bike was in our shop, this is exactly the way I would repair it.

:bigt


Don't hide 'em, Ride 'em !!

RF Whatley
Cornelia, GA
Re: Hole where you don't want one
RF Whatley #216709 10/02/08 11:40 pm
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Thanks RF I needed to hear that I'll flush it very well and see about a filter strait away! Once again Thanks!


I can fix any thing with a bigger hammer
64-71 Triumph Bitsa
Re: Hole where you don't want one
John Michl #216716 10/03/08 12:13 am
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John -
I just saved you 10 months and $600. Can you see your way clear to send me $300 ??

laughing


Don't hide 'em, Ride 'em !!

RF Whatley
Cornelia, GA
Re: Hole where you don't want one
RF Whatley #216740 10/03/08 7:10 am
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Thats an awesome read.

Originally Posted by Right from that site....
"A hole in the middle of the piston, particularly a melt ed hole in the middle of a piston, is due to the extreme heat and pressure of pre-ignition."


"When I examined myself and my methods of thought, I came to the conclusion that the gift of fantasy has meant more to me than my talent for absorbing positive knowledge." ~Albert Einstein
Re: Hole where you don't want one
GavinJuice #216774 10/03/08 1:44 pm
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Cycle Magazines technical editor, Kevin Cameron, has written extensively about "toughening a motor to pre-ignition." While the common practice of being sure there are no sharp edges inside the combustion chamber: valve pocket edges, spark plug threads, head gaskets over hanging combustion chamber and thin valve margins are often overlooked by the inexperienced motor builder; many modern performance machine shop and assembly practices also increase the chances pre-ignition will occur.

Building a motor is an exercise in learning how to manage heat. The heat created through combustion must be removed from the parts involved: Valves, pistons, guides, spark plugs, piston and the rings. Failing this, the heat builds up to a point where some one of these becomes hot enough to act as a glow plug and cause pre-ignition.

Modern automobile engineers go to great lengths to provide adequate cooling around the valve seats and cylinder bores. They spend a lot of time making sure the valve seats remain Concentric and round, and the cylinder bores remain true. If heat isn't extracted from the piston, through the rings and into the cylinder walls and heat extracted from the head of the valve through it's seat and into the head we can have the seeds of pre-ignition. This extends to making sure the valve seat remains round and Concentric to the head of the valve something often overlooked by people building these old air cooled motors. The margins, or edges, of the valves must not be thinned to increase flow or clearance increasing the chances they will become glow plugs.

The fins of our old air cooled engines can handle just so much heat. If the unwary owner is sold a performance valve job where the valve seat contact area is limited, the head of the valve will not be able shed the required amount of heat. I recommend that the exhaust valve seat be .080" wide, and the intake be .060" wide when used with today's "pump" gasoline. Narrowed valve seats, where the exhaust seat is often as little as .040" wide, increase the chances the valve will become a glow plug and promote pre-ignition.

If the rings are not broken in, with full contact with the cylinder walls, the piston too will retain too much heat. This increases the chance the sharp edge of a machined valve pocket will become a glow plug and promote pre-ignition. Of course all this goes for the spark plug and any exposed threads. When the rings are not sealing, and there is some indication of this here by the shiny oil all over the top of both of the pistons in the picture, the oil that gets into the combustion chamber lowering the effective octane rating of the incoming gasoline. I see a lot of low mileage pistons seizures from detonation and holes in pistons from pre-ignition in low mileage rebuilds. In most cases there are signs that the rings had not seated and insured an adequate heat path to cool the piston.

So while building a motor one should keep in mind how one is going to get rid of the normal heat of combustion, BUT one must also keep in mind not to create a situation where there is "abnormal" amounts of heat. It starts with the selection of a compression ratio to match the "worst" octane rating of the gas you think will be available in the area you are going to use the motorcycle. This often means the standard factory compression ratio is too high as with the case of the early T140's.
One must also make sure they hit all the basic marks with timing, and carburation.

Toughening ons of these air cooled motors to the ravages of pre-ignition is an exercise in the basics: Prevent situations where there is abnormal heat by keeping the bike in tune, use gasoline with an octane rating that will protect the motor from detonation, provide a heat path out of the motor through the rings and valve seats that is large enough to do the job and keep the motor in an rpm range where there isn't excessive cylinder pressure - lugging the engine. Simple eh ;-)

I hope this gives you something to think about and you will further explore some of the issues with detonation and pre-ignition...
John
Oh, personally I would take it apart and clean it properly given the oil pump's propensity to stop returning oil to the tank when it gets a tiny bit of piston swarf under the check ball in the return side of the pump. At least it isn't a gear pump where all of the aluminum bits would lap or jamb in the teeth.


Re: Hole where you don't want one
John Healy #216818 10/03/08 5:38 pm
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John, I don't know what else I can do. 1. It's not 'hi-performance' engine. you seen the heat damage I poster long ago the engine was bored from 20 over to 30 over new pistons and rings from Baxters. I did nothing to the head ( I cleaned it. It was running on pump gas 86 octane I don't remember it might have been 89. The pipes didn't turn blue it didn't run long enough to do a plug read! How the heck you supposes to know its getting to hot (I heard no pinging, that I'm aware) "It starts with the selection of a compression ratio to match the "worst" octane rating of the gas you think will be available in the area you are going to use the motorcycle." How do you do that? I didn't buy H/P pistons. And I did nothing to the head. I didn't look to me like it needed any . Befor:
[Linked Image]
After
[Linked Image]
If it my fault for not using jet fuel, Is it my fault for not having the head re-done? Maybe? I know this It was put together with care and with detail. Granted I pale in most regards as i engine builder but DAMN I would life to have gotten more than 25 miles out of it!


I can fix any thing with a bigger hammer
64-71 Triumph Bitsa
Re: Hole where you don't want one
John Michl #216824 10/03/08 5:55 pm
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John you once said that this
[Linked Image]
was heat related now I have this
[Linked Image]
same side same engine different heat or is there something going on here?


I can fix any thing with a bigger hammer
64-71 Triumph Bitsa
Re: Hole where you don't want one
John Michl #216867 10/03/08 10:40 pm
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John: "Same side same engine different heat or is there something going on here?"

Trying to explain this so it could be understood in this format and time available to me is challenging, but here goes:

Some of the answer to this question will be answered when you remove the gudgeon/wrist pin. I am guessing here, but by looking at the area of the piston in distress that the pin will NOT show a lot of heat distress. I think this was a fairly quick event and not as a result of a long slow soaking build up of heat from extend periods of detonation. The pin might just be the same silver color or a light straw and not show the typical dark blues or purples associated with heavy detonation.

The piston is lacking the distress fore and aft of the pin boss (often called a 4 corner seizure) typically present when the failure is purely detonation. The distress is localized just under the oil ring on the thrust face which tells me that the process happened quickly. I am pretty sure this is a case where the rings didn't seat or "break-in." Just look at the top of the pistons. They are coated with a film of oil.

Check the face of the rings to see if there is a continuous polished surface from one end of the ring gap to the other. There should be no breaks or signs of distress. Do this for all three rings, especially on the piston that didn't seize. If the ring isn't in contact with the cylinder wall you have no heat, or limited heat transfer out of the piston.

If the pre-ignition happened because of valve or spark plug, the damage would have happened so fast as to not give the piston time to heat up and you would not have seen the seizure below the oil ring and the pin would come out bright silver as new. I think it was the build up in heat in piston itself that caused the pre-ignition and it picked the edge of the valve pocket to do it.

So lets leave all this and make a few suggestions to help prevent this. When I was young you could make all sorts of errors during assembly and the high octane rating of the available gasoline would prevent what today would cause this problem. If the rings didn't break-in and some oil got into the chamber it wasn't the problem it is today. So if you are not comfortable with your skills it isn't a bad idea to use a tank of race gas to break in the motor. It gives you a little margin of error until the rings break-in.

That said if the motor shows any signs of oil consumption during break-in I WOULD PERSONALLY install a new set of rings and go through the break-in process again. I have never seen a Triumph "break-in" a set of rings once they failed to do so immediately upon start up. The margin for error is not what it once was!!!

I would match the ring to the coarseness of the honing stones used to prepare the cylinder. A lot of modern motorcycle and automotive machine shops do not have honing stones coarse enough to be used with grey cast iron rings. They will use the fine grit stones required by steel or ductile iron rings.

The typical grey cast iron rings are not lapped round at the factory and are designed to be "honed" by the surface of the cylinder during break-in. This requires a surface you would get using stones of a 150 to 220 grit.

In the day when this bike was made a 150 grit stone was considered finishing and worked well with the grey cast iron rings. Today that same stone would have "roughing" printed on the box and would NEVER be used to prepare a cylinder for ductile iron or steel rings. They require surface finishes of 280 and smoother, almost polished. Few automotive machine shops even have 220 grit, let alone 150 grit stones in the shop.

If modern cylinder finishes of smoother than 220 are used with grey cast iron rings you risk problems unless everything else is right, you have gasoline with enough octane to handle the task and aggressive break-in procedures are used.

Now we are not finished! Modern oil is blended to let the motor get better gas mileage by being very slippery. This isn't something you want when you are trying to break-in a set of grey cast iron rings. In the UK you can buy 10 different brands of "break-in" oil that has little, if any additives (you do want anti-oxidants to prevent the parts from rusting). In the US they make it harder. If you can find it you want to get oil with an SAE rating of CD or lower. This makes the additive package similar to what was available when the bike was made.

Also many of us have gone to what I like to call "drier" assembly. This is where we lube the wrist pin with assembly lube. Then we wash the cylinder in HOT soapy water and scrub it until white rag comes out absolutely clean. Be patient as this takes time. The I put a small amount of oil on a lint free rag or paper towel and rub the oil on the cylinder walls. I put a drop or so of oil on the thrust faces of the piston and leave the RINGS DRY.

I the use a aggressive break-in. I verify that the oil pump is circulating oil and run the bike up through the gears briskly reaching 4 to 5,000 rpm in each gear. Just the once and follow through with a typical break-in period, being sure not to lug the motor!!!!! These motor like some rpm's!!!!

Now I am begging the question here, but I cannot under emphasize the importance that every thing else be right: carburetor, timing, etc.

And yes, the compression ratio of these "stock" pistons was too high for the existing conditions: Modern low octane fuel, oil in the combustion chamber, lack of heat transfer out of the top of the piston through the rings - some 75% plus of the heat in a piston is transferred to the cylinder walls through the rings!

This hits the high spots as being a mechanic has changed a lot for me in the past 50 years I have been doing it.
John

Re: Hole where you don't want one
John Healy #216900 10/04/08 2:31 am
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Not to discount the excellent advice of other posters, but two piston failures on the same side within short order would make me highly suspicious of air leaks or ign. problems unique to that side. Cracked head...air leak when it warms up?


77 T140V
79 T140D
Re: Hole where you don't want one
bt908 #216926 10/04/08 8:14 am
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What about your plugs? Post pictures of those from the corresponding cylinders.


"When I examined myself and my methods of thought, I came to the conclusion that the gift of fantasy has meant more to me than my talent for absorbing positive knowledge." ~Albert Einstein
Re: Hole where you don't want one
GavinJuice #216965 10/04/08 2:02 pm
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Rarely, In this kind of situation, will the spark provide any information as to conditions just prior to the pre-ignition... the cause. It will most likely be coated with oil, as are both tops of the pistons, and it will illustrate distress incurred as the pre-ignition was happening.

The one thing you can look at on the spark plugs is the color of the first few threads as they will give you an idea as to how hot the plug was running. You can also compare them with the threads of the other plug.

You should also look carefully at the contact face of the rings on both pistons. All of the ring's wear surfaces that rub on the cylinder should show 360° contact. Any less and you have a preparation, assembly or break-in problem.

You should also examine the color of the wrist pin. It indicates the temperature of the metal just before the incident. In an engine that is running normally - good ring heat transfer and no detonation, the pin will look just like it did when it came out of the box.

Check the pins and rings on both sets of pistons, and on the set of pistons from the set of pistons.

With modern oil, modern gasoline AND MODERN machine shop practices one does not have the margin for error as we once did!!!!! It is amazing how real high "motor" octane number (the M in R+M/2) makes you look like a real engine builder. You didn't even have to know what you were doing...

This is not a new problem and you are not the only one to have gone through it several times. Experienced dealers during the 1980's had similar adventures before they came to grips with the factors at work. There was a time where I would get 10 calls a week from dealers who were having the same problems you are experiencing. I can't tell you how many times I have heard, "I have been doing this for 20, 30 or 40 plus years and never had this problem!"

AND YES, it goes without saying you must check the basics... although I am confident you did that the last time.
John

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